Filter apparatus

Abstract

A filter apparatus includes input and output terminals, a ground terminal, a ground electrode connected to the ground terminal, a plate electrode, and first to four lines. A multilayer body of the filter includes a first and second main surface. The input and output terminals and the ground terminal are provided on the second main surface. The plate electrode is closer to the first main surface than the ground electrode. The first line is electrically connected to the input terminal and the plate electrode. The second line is electrically connected to the output terminal and the plate electrode. The first line is capacitively coupled to the second line. When the multilayer body is viewed in a plan view from a layering direction, the plate electrode covers a portion of a space providing capacitive coupling between the first line and the second line.

What is claimed is: 
     
         1 . A filter apparatus comprising:
 a multilayer body including a plurality of dielectric layers that are layered, the multilayer body including a first surface and a second surface;   an input terminal, an output terminal, and a ground terminal provided on the second surface;   a ground electrode connected to the ground terminal;   a plate electrode provided closer to the first surface than to the ground electrode;   a first line electrically connected to the input terminal and the plate electrode;   a second line electrically connected to the output terminal and the plate electrode;   a third line and a fourth line connecting the plate electrode and the ground terminal to each other; and   a first capacitor electrode and a second capacitor electrode between the plate electrode and the second surface, and connected to the first line and the second line, respectively; wherein   the first line is capacitively coupled to the second line; and   when the multilayer body is viewed in a plan view from a layering direction;
 the plate electrode covers a portion of a space providing capacitive coupling between the first line and the second line; 
 the first capacitor electrode and the second capacitor electrode partially overlap with each other; and 
 the plate electrode covers the first capacitor electrode and the second capacitor electrode. 
   
     
     
         2 . The filter apparatus according to  claim 1 , wherein
 when the multilayer body is viewed in the plan view from the layering direction, the first capacitor electrode and the second line partially overlap with each other.   
     
     
         3 . The filter apparatus according to  claim 1 , wherein
 when the multilayer body is viewed in the plan view from the layering direction, the second capacitor electrode and the first line partially overlap with each other.   
     
     
         4 . The filter apparatus according to  claim 1 , further comprising:
 a third capacitor electrode between the plate electrode and the second surface; wherein   when the multilayer body is viewed in the plan view from the layering direction:
 the third capacitor electrode partially overlaps with both of the first line and the second line; and 
 the plate electrode covers the third capacitor electrode. 
   
     
     
         5 . The filter apparatus according to  claim 1 , wherein
 when the multilayer body is viewed in the plan view from the layering direction:
 at least a portion of the first line overlaps with the second line; and 
 the plate electrode covers a portion where the first line and the second line overlap with each other. 
   
     
     
         6 . The filter apparatus according to  claim 1 , further comprising:
 a fourth capacitor electrode connected to the first line and opposed to the plate electrode; and   a fifth capacitor electrode connected to the second line and opposed to the plate electrode.   
     
     
         7 . The filter apparatus according to  claim 1 , further comprising:
 an LC series resonator between the plate electrode and the ground electrode; wherein   the LC series resonator includes:
 a sixth capacitor electrode opposed to the ground electrode; and 
 a fifth line connected to the sixth capacitor electrode and the plate electrode. 
   
     
     
         8 . The filter apparatus according to  claim 1 , further comprising:
 an LC series resonator between the plate electrode and the ground electrode; wherein   the LC series resonator includes:
 a seventh capacitor electrode opposed to the plate electrode on a side closer to the second surface than to the plate electrode; and 
 a sixth line connected to the seventh capacitor electrode and the ground electrode; and 
   when the multilayer body is viewed in the plan view from the layering direction, the plate electrode further covers the seventh capacitor electrode.   
     
     
         9 . The filter apparatus according to  claim 6 , further comprising:
 an LC series resonator between the plate electrode and the ground electrode; wherein   the LC series resonator further includes:
 an eighth capacitor electrode closer to the second surface than to the plate electrode; and 
 a seventh line connected to the eighth capacitor electrode and the ground terminal; and 
   when the multilayer body is viewed in the plan view from the layering direction, the plate electrode further covers the eighth capacitor electrode.   
     
     
         10 . The filter apparatus according to  claim 9 , wherein, when the multilayer body is viewed in the plan view from the layering direction, the eighth capacitor electrode is between the fourth capacitor electrode and the fifth capacitor electrode. 
     
     
         11 . The filter apparatus according to  claim 10 , wherein the eighth capacitor electrode is provided in a same dielectric layer as the fourth capacitor electrode and the fifth capacitor electrode. 
     
     
         12 . The filter apparatus according to  claim 9 , wherein, when the multilayer body is viewed in the plan view from the layering direction, the eighth capacitor electrode partially overlaps with the fourth capacitor electrode and the fifth capacitor electrode. 
     
     
         13 . The filter apparatus according to  claim 1 , wherein
 the first line includes:
 a first interconnection pattern provided in a dielectric layer in the multilayer body; 
 a first via that connecting the first interconnection pattern and the input terminal to each other; and 
 a second via that electrically connecting the first interconnection pattern and the plate electrode to each other; and 
   the second line includes:
 a second interconnection pattern provided in a dielectric layer in the multilayer body; 
 a third via that connecting the second interconnection pattern and the output terminal to each other; and 
 a fourth via that electrically connecting the second interconnection pattern and the plate electrode to each other. 
   
     
     
         14 . The filter apparatus according to  claim 1 , wherein
 the first and second capacitor electrodes are included in a plurality of capacitor electrodes;   the plurality of capacitor electrodes at least partially define at least one capacitor;   the at least one capacitor includes a capacitor connected between the input terminal and the output terminal;   the first line, the second line, the third line, and the fourth line are included in a plurality of lines;   the plurality of lines at least partially define a plurality of inductors;   the plurality of inductors include inductors connected in series between the input terminal and the ground terminal; and   the plurality of inductors include additional inductors connected in series between the output terminal and the ground terminal.   
     
     
         15 . The filter apparatus according to  claim 14 , wherein the plurality of inductors include a bridge inductor including a first end connected between a pair of the inductors and a second end connected between a pair of the additional inductors. 
     
     
         16 . The filter apparatus according to  claim 1 , wherein
 each of the input terminal, the output terminal, and the ground terminal are flat plate electrodes; and   the ground terminal includes a plurality of ground terminals arranged along two long sides on the second surface.   
     
     
         17 . The filter apparatus according to  claim 1 , wherein
 the plate electrode has a C shape or substantially a C shape when viewed in the plan view from the layering direction; and   the ground electrode is in an H shape or substantially in an H shape when viewed in the plan view from the layering direction.   
     
     
         18 . The filter apparatus according to  claim 1 , wherein
 the first and second capacitor electrodes are included in a plurality of capacitor electrodes;   the plurality of capacitor electrodes at least partially define at least one capacitor;   the at least one capacitor includes a capacitor connected between the input terminal and the output terminal;   the first line, the second line, the third line, and the fourth line are included in a plurality of lines;   the plurality of lines at least partially define a plurality of inductors;   the plurality of inductors include first inductors connected in series with a first additional capacitor between the input terminal and the ground terminal; and   the plurality of inductors include second inductors connected in series with a second additional capacitors between the output terminal and the ground terminal.   
     
     
         19 . The filter apparatus according to  claim 1 , wherein
 the first and second capacitor electrodes are included in a plurality of capacitor electrodes;   the plurality of capacitor electrodes at least partially define at least one capacitor;   the at least one capacitor includes a capacitor connected between the input terminal and the output terminal;   the first line, the second line, the third line, and the fourth line are included in a plurality of lines;   the plurality of lines at least partially define a plurality of inductors;   the plurality of inductors include first inductors connected in series between the input terminal and the ground terminal;   the plurality of inductors include second inductors connected in series between the output terminal and the ground terminal;   the plurality of inductors include third inductors connected in series between a pair of the first inductors and a pair of the second inductors; and   the plurality of inductors include a fourth inductor connected between a pair of the third inductors and the ground terminal.